A communication transceiver allows a two-way, or bidirectional, communication through a shared medium, such as a microwave radio link, a satellite channel, a fiber optic cable, a hybrid fiber optic cable system, or a copper cable to provide some examples. The communication transceiver may include a transmission amplifier, such as a power amplifier (PA), with enough drive capability to generate strong transmitter waveforms and a reception amplifier, such as a low noise amplifier (LNA), with suitable fidelity to boost weak received signals. The transmission amplifier and the reception amplifier are often impedance-matched to the shared medium, especially at higher frequencies, requiring a mechanism to couple the transmission amplifier and the reception amplifier to the shared medium.
These mechanisms often depend on characteristics of the shared medium and the design of the communication system. Frequency diplexers and circulators are some common techniques used at radio frequencies (RF). Frequency diplexers are not appropriate for connecting the transmission amplifier and the reception amplifier to the shared medium when a common frequency band is shared for transmit and receive functions. Likewise, circulators are large in size and may become too costly at RF. Another common technique used at RF are transmit/receive switches. In this technique, the transmission amplifier and the reception amplifier are coupled to the shared medium via one or more transmit/receive switches. The transmit/receive switches coupled either the transmission amplifier or the reception amplifier to the shared medium.
A transmit/receive switch with adequate performance may be difficult to integrate into an RF integrated circuit (IC). For example, high-speed Field Effect Transistors (FETs) switches may not be available in a pure bipolar process. If the switch is available, it may not have adequate frequency response or too much loss. The high voltage swings of the transmission amplifier may force some components of an integrated transmit/receive switch design to exceed the maximum voltage limits of the IC process. As a result, the transmit/receive switches often remain an external component, often with an increased cost, to the IC for this reason.
Thus, there is a need for an apparatus and/or a method to couple the transmission amplifier and the reception amplifier to the shared medium that overcomes the shortcomings described above. Further aspects and advantages of the present invention will become apparent from the detailed description that follows.
The present invention will now be described with reference to the accompanying drawings. In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. The drawing in which an element first appears is indicated by the leftmost digit(s) in the reference number.